1. Research and Development Group; Hitachi, Ltd.; 1-1, 7-Chome, Omika-cho, Hitachi Ibaraki 319-1292 Japan
2. Magnetic Materials Research Laboratory; Hitachi Metals, Ltd.; 15-17, 2-Chome, Egawa, Shimamoto-cho, Mishima-gun Osaka 618-0013 Japan
3. Department of Materials Science and Engineering; Kyoto University; Yoshida-honmachi, Sakyou-ku; Kyoto 606-8501 Japan